1. Field of the Invention
The present invention relates generally to magnetic recording and reproducing apparatus and more particularly, to a video recorder/reproducer tape transport employing spring-loaded guides intermediate the take-up reel and the capstan and intermediate the scanner head assembly and the supply reel for controlling the tension on the tape.
2. Description of the Prior Art
Tape transports for use in magnetic tape recording and reproducing of high frequency electronic signals are well known. Such transports generally include a tape deck with supply and take-up reels for storing the magnetic tape. The reels are rotatably supported on the tape deck on opposite sides of a transducer adapted to transduce electrical signals to and/or from the magnetic tape. A rotatable drive capstan, mounted to the deck, operates to drive the tape at a predetermined speed between the supply and take-up reels. The tape is guided over the transducer between the supply and take-up reels by an arrangement of guides. For recording and reproducing high frequency signals such as video signals, the transducers are mounted on a rotatable circular scanner assembly, which in turn is mounted to the tape deck. The rotational speed of the scanner and the tape speed each assist in providing the head-to-tape speed necessary for recording and/or reproducing video signals. The scanning assembly generally includes one or more transducing heads which operate to translate electrical signals to magnetic variations for storage on the tape during the record operation or which operate to translate magnetic signals from the tape into the original signal during the reproduce operation.
In recording and reproducing broad band signals on magnetic tape, a helical wrap type of scanning assembly is often used. Basically, such a scanning assembly includes a pair of coaxial, cylindrical drums of aproximately four to six inches in diameter. The drums are axially spaced to define an annular gap therebetween. The drums support one or more transducer heads which are used to record and/or reproduce signals from the tape. Magnetic tape, generally of approximately one inch width, is wrapped helically about the drums and is moved over the drums in the direction of its length. The transducer heads are rotated in the gap between the drums and sweep a rectilinear area extending at an acute angle across the tape. As a result, relatively long tracks extending at acute angles to the edge of the tape are successively spaced along the tape. In the recording and playback of television signals, an entire field or, in some instances, an entire frame may be included in one of the relatively long tracks.
Many prior art transports have a tape path wherein the tape is wrapped substantially 360.degree. in helical fashion about the scanning assembly. In one type of tape wrap, known as the Omega wrap, the tape approaches and leaves the surface of the scanning assembly at approximately the same point and forms a loop about the scanning assembly approximating the shape of the Greek letter "capital Omega".
In one prior art helical wrap-scanning assembly, two vacuum chambers are included to control the quantity and tension of tape available at the scanner. The vacuum chamber tends to isolate speed and tension disturbances in the tape supplied by the supply reel. There are numerous causes of disturbances in the tape as it is supplied from the supply reel. For example, such disturbances occur when the tape scrapes a flange of the reel or has an irregularity in its structure, when the brush friction varies, when the reels are eccentric, etc. However, vacuum chambers require a vacuum source. Thus, vacuum chamber transports are relatively large, produce an audibly distracting noise during operation and are relatively expensive. An example of a video recorder employing helical wrap-scanning assembly and a vacuum system is found in my earlier U.S. Pat. No. 3,898,693, entitled "Video Recorder/Reproducer Transport Using Vacuum Columns and Servos".
Another type of transport that is extensively used for television broadcast recording and reproducing is one commonly referred to as the "quadruplex" recorders. Such a transport includes a rotary head assembly with four transducers mounted thereon that transverses the tape in a direction at right angles to the edges of the tape. Quadruplex recorders have been found to produce pictures of good quality. However, the complexity and costs of quadruplex recorders have been substantially greater than that of helical wrap type recorders. Also, the operating costs, wear of transducers and wear of tape of quadruplex recoders are substantially greater.
Thus, heretofore in many instances it has been a trade off of quality versus costs in determining whether to use quadruplex or helical scan format type transports. As a result, the quadruplex transport has been more widely used for broadcast purposes where picture quality is of prime concern. The helical scan transport has found more use in educational, industrial and communication applications which do not require the picture quality level demanded by the broadcast industry.
In video tape recorder/reproducers of the helical scan format, tension control of the tape is important due to the excessive tape friction in the tape path. Therefore, the tape tension should change whenever the tape direction changes. For example, when tape is being transferred from the supply reel to the take-up reel, the tension at the supply reel should be low relative to the tape tension at the take-up reel. This will allow the capstan to drive the tape easier and tension in the tape path will not be so high as to damage the tape. For similar reasons, when the tape is rewound from the take-up reel to the supply reel, the tape tension at the supply reel side should be high relative to the tape tension at the take-up side.